1. Opennurbs: What is openNURBS?

The openNURBS Toolkit reads and writes all Rhino 3DM files. Additionally, the openNURBS Toolkit provides NURBS evaluation tools and elementary geometric and 3D view manipulation tools.

2. OpenCascade : opencascade

OpenCascade提供二维和三维几何体的生成、显示和分析。主要功能有：
1．创建锥、柱、环等基本几何体；
2．对几何体进行布尔操作（相加，相减，相交运算）；
3．倒角，斜切，镂空，偏移，扫视；
4．几何空间关系计算（法线，点积，叉积，投影，拟合等）；
5．几何体分析（质心，体积，曲率等）；
6．空间变换（平移，缩放，旋转）;

3. CGAL: CGAL

The library offers data structures and algorithms like triangulations, Voronoi diagrams, Boolean operations on polygons and polyhedra, point set processing, arrangements of curves, surface and volume mesh generation, geometry processing, alpha shapes, convex hull algorithms, shape reconstruction, AABB and KD trees…

4. Verb-Nurbs: What is verb?

verb is a library for creating and manipulating NURBS surfaces and curves in many languages including JavaScript.
verb provides advanced tools like derivative evaluation, adaptive tessellation, and intersection. Verb provides a concurrent execution runtime via WebWorkers in modern browsers and thread pools on other platforms and is suitable for use in a datacenter or in the browser.
verb is not a graphics library. It nicely compliments web graphics libraries like three.js, but is happy to live without one.

5. BRL-CAD: BRL‑CAD

Hybrid CSG and B-REP kernel with innovative methods for unambiguous 3D geometry. Verification, validation, performant.

6. Intersection algorithms

https://www.sintef.no/projectweb/computational-geometry/

7. GoTools: GoTools

GoTools is the name of a collection of C++ libraries related to geometry. The libraries are organized as a core module with additional modules added on top. The core module contains generic tools and spline functionality. The additional modules contain functionality for intersections, approximative implicitization, parametrization, topology, and more.

8. SISL:

SISL is a comprehensive NURBS library for the modeling and interrogation of curves and surfaces. It is implemented in C and has been under continuous development over two decades.